Well I guess one shouldn't really be offended by a song's words or sentiments when the song expresses what WAS a understanding of life at a point in the past.
If the song was written with the intent to offend or was written with some sort of "in-your-face" justification (on the part of the author) it is offensive, period!
I know songs whose words are painfully racist. But in the context of the times when they were written and performed they were done "in the vernacular" so to speak.
I personally would not sing these songs as they were written and if I couldn't edit them so they still had value as musical entertainment I wouldn't sing them at all.
Pete Seeger was involved with the re-issue, on a LP, of a number of Uncle Dave Macon's recordings. Some racist words are part of the songs. Pete Seeger is no racist. He provided a valued service by helping to re-issue the songs. I play a lot of Uncle Dave's stuff and never use the racist words and the songs still stand strong.
There is a terrible racist word and racist sentiment in "Prohibition is a Failure". There are offensive words in the "Jim Crow" novelty songs from before during and after the Civil War. "Suananoa Tunnel" has a verse with a racist word in it. "Watermellon on the Vine" I think also has racist words (I'm a bit fuzzy here since I never learned that one). These songs are not, in themselves, racist.
I heard a song when I lived in Alabama, which was definately racist. It was a song sung by a mamber of the Klan, to the tune of "Battle Hymn of the Republic".
That earlier song alanabit, (If memory serves me) was objectionable because while it may have had legitimacy in the past it certainly shouldn't be taught to a child today.